Question: $\overline{AB} = 2\sqrt{13}$ $\overline{AC} = {?}$ $A$ $C$ $B$ $2\sqrt{13}$ $?$ $ \sin( \angle BAC ) = \frac{3\sqrt{13} }{13}, \cos( \angle BAC ) = \frac{2\sqrt{13} }{13}, \tan( \angle BAC ) = \dfrac{3}{2}$
$\overline{AB}$ is the hypotenuse $\overline{AC}$ is adjacent to $\angle BAC$ SOH CAH TOA We know the hypotenuse and need to solve for the adjacent side so we can use the cos function (CAH) $ \cos( \angle BAC ) = \frac{\text{adjacent}}{\text{hypotenuse}} = \frac{\overline{AC}}{\overline{AB}}= \frac{\overline{AC}}{2\sqrt{13}} $ $ \overline{AC}=2\sqrt{13} \cdot \cos( \angle BAC ) = 2\sqrt{13} \cdot \frac{2\sqrt{13} }{13} = 4$